Although the Digimon franchise started around the same time as Pokemon, its roster has always been somewhat larger due to new digital monsters frequently being created outside the video games and anime series. As such, there are many different Digimon species, and some have their names changed between different languages.
Because there are only so many names that can work well with the -mon suffix at the end, some Digimon have names that are strange, repetitive, ill-fitting, generic, or just plain bad. Although not all these Digimon are well-known as others, their names still deserve a spot in Digimon history.
10 MarineAngemon
MarineAngemon is a fine Digimon based on Sea Angels, but it's not related to the Angemon family at all, so why not call it something else? Since it lives in the Net Ocean, the Marine part of its name is still fitting. Since it uses attacks involving cuteness or positive emotions and pacification, MarineLovemon or MarinePeacemon would be better names than MarineAngemon. Alternatively, the Marine part of its name could be removed instead, and it could be called Loveandpeacemon. As it is now, it seems like the creators of MarineAngemon went with the first name that came to mind.
9 Omnimon Zwart
Omnimon Zwart is the DNA digivolution of BlackWarGreymon and BlackMetalGarurumon, so one would think its name would be BlackOmnimon just for consistency, but instead, it's called Omnimon Zwart. Zwart is just the German word for black, so it sounds like they just slapped the first thing they thought of onto the Digimon.
Why randomly choose another word for the color "black" when both Digimon involved and all of their previous forms have it in their names already? There isn't anything else new or unique about this Digimon, so it just makes it seem a bit pretentious.
8 Leopardmon Leopard Mode
Leopardmon belongs to a group called the Royal Knights and, in Japanese, goes by the name Duftmon. Duftmon can also mode change into Leopard Mode, where he looks a little more similar to his namesake. Since Duftmon's name was changed to Leopardmon in English, one would think Leopard Mode would have been changed to Beast Mode or Animal Mode, but instead, it's just Leopardmon Leopard Mode.
Why even change the name at all at that point? There's nothing inherently wrong with the name Duftmon, although using the Danish word for "fragrance" is a little weird for a Digimon completely unrelated to the term. Maybe it smells lovely and we have no idea.
7 Apocalymon Creepy Mode
Apocalymon Creepy Mode is probably one of the most unnecessary Digimon names ever. Apocalymon was the final villain in the original Digimon Adventure anime series and didn't actually have an alternate mode - Creepy Mode was originally just a card made for the Digi-Battle Card Game that focuses on the humanoid upper half of Apocalymon's body.
Apocalymon is already creepy-looking; it didn't really need a Creepy Mode, especially since it's not even a different Digimon.
6 Cherubimon
Due to the promo cards and other English media involving the first Digimon movie, Cherubimon was once known to western fans as Kerpymon, which seems like a mistranslation. Still, the name Cherubimon doesn't fit well with this Celestial Digimon's rabbit-like appearance. Cherubimon seems like it would be a better name for Lucemon since it has more in common with cherubs in terms of appearance.
Alternatively, they at least could have called Cherubimon Evil/Vice Kerpymon and then have Cherubimon Good/Virtue remove the extra word in its name. To be fair, a more literal name like Godrabbitmon wouldn't be a great choice either.
5 Scorpiomon
Scorpiomon is another case where the original Japanese name should have been kept instead of being changed, not because Scorpiomon is a lousy name, but because the name Scorpiomon was used later for another Digimon. Scorpiomon's original Japanese name is Anomalocarimon, based on an extinct genus of anthropods called Anomalocaris, similar to the fossil Pokemon Anorith.
Years later, when the real Scorpiomon was created, its English name was changed to SkullScorpionmon. While SkullScorpiomon isn't a bad name since it has a skeletal appearance, it and Anomalicarimon are seemingly unrelated. Both are just based on similar creatures and have bladed tails.
4 Flybeemon
An interesting fact about insect Digimon is that there is not one named Beemon, which is possible to avoid confusion with Veemon. However, there is a Honeybeemon, Stingmon, Flymon, FanBeemon, CannonBeemon, and Flybeemon. The latter is a cross between a dragonfly and a bee, so why not name it Dragonbeemon instead?
It sounds better and seems less repetitive than Flybeemon. Flybeemon is even based on a type of wasp called an Ichneumon wasp, which already has "mon" in its name! While a Digimon named Waspmon does exist, Flybeemon was created years before it, so it's strange it didn't get the name first.
3 MaloMyotismon
Myotismon is one of the most well-known and prominent villains in the Digimon Adventure series, and when it turned out he was the final villain of Digimon Adventure 02, fans had mixed feelings. While in Japanese, Myotismon's new form is called BelialVamdemon, continuing the trend of demonic references that started with VenomMyotismon; his English name is MaloMyotismon. Myotismon had been primarily seen as a villain, and adding the Spanish word for bad to his name is like if Lex Luthor started calling himself EvilBadVillainman. MaloMyotismon is just one of those cases where they should've kept part of the original name.
2 Monmon
There have been various Digimon based on monkeys and apes, such as Apemon, Gorillamon, Etemon, and Makuramon, but Monmon has the worst name. Monmon's Japanese name is Koemon, in which the word Ko means child and Etekoe means monkey, using the other half of the word Etemon's name is based on, despite not being related.
It makes sense that Koemon would be translated to Monmon, but it just isn't a great name for a Digimon, and it should have been called Monkeymon instead since there has somehow been no Digimon with that name yet. Monmon just doesn't sound right.
1 Agumon Expert/Fake Agumon Expert
Agumon Expert is an exceptionally intelligent Agumon that received a doctorate from the Digital World Academy, a university in the Digital World, so why not just call it DoctorateAgumon, ProfessorAgumon, or even just ExpertAgumon instead? Agumon Expert makes it sound like it increased its difficulty level.
Even worse is Fake Agumon Expert, a less knowledgeable Agumon that spreads misinformation, which could have and should have been called FakeExpertAgumon instead. Alternatively, maybe if Agumon expert was called DoctorateAgumon, Fake Agumon Expert could be called PlagiaristAgumon or something along those lines, since it plagiarized off the real Agumon Expert's work after all.